The present invention relates to equipment for moving the roll of a paper machine, which roll is arranged to be moved in an axial direction, and which equipment includes                a cradle arranged to move, which is intended to be attached to the roll,        two pairs of masses, which are supported rotatably on the cradle,        a drive shaft in each of the pairs of masses, for rotating the pairs of masses,        drive devices for rotating the drive shafts in the desired phase, which drive devices include a motor and drive-train means fitted to the drive shafts,        the drive-train means include a pair of intermeshed gears, which are arranged in connection with the drive shafts, in order to rotate the drive shafts using a single motor, and        the drive-train means include an adjustment element for creating and adjusting the phase difference of the drive shafts.        
The equipment described in the introduction is used in a paper machine, particularly for oscillating a so-called breast roll. In other words, the breast roll, which is arranged to support the wire, is moved in its axial direction. In a fourdrinier-wire machine, the fibre suspension is fed onto the wire precisely at the breast roll, so that moving the breast roll makes the wire too move in the cross-direction of the paper machine. The fibre suspension will then spread evenly over the wire.
On account of the magnitude of the mass being moved and the frequency used, simple operating devices, such as hydraulic cylinders, are unsuitable for this purpose. In addition, the use of hydraulic cylinders would induce large forces in the foundations of the paper machine. Thus, in modern equipment, the so-called center-of-gravity principle is used, which is implemented with the aid of two pairs of masses arranged to rotate. Each pair of masses is formed of two eccentric masses, which are mutually synchronized. The axes of rotation of the pairs of masses are at right-angles to the axis of rotation of the breast roll and the pairs of masses are mounted in bearings in a special cradle. The working motion of the equipment is created by arranging a suitable phase difference in the rotating pairs of masses. In addition, the length of the working motion can be adjusted by altering the said phase difference. When they are in completely opposing phases, the pairs of mass cancel out each other's effect, so that the cradle remains stationary.
One known apparatus is disclosed, for example, in WO publication 98/35094. In the apparatus, the pairs of masses are rotated by two electric motors, which are regulated separately to create the desired phase difference. This allows the length of the working motion to be adjusted. In practice, two frequency converters are required to make the adjustment, as well as effective control software together with peripheral devices.
In addition, in order to ensure sufficient regulation tolerance, high-power special electric motors are required. Thus, the equipment becomes complicated and expensive, especially in the case of the automation and the electric motors. In addition, the pairs of masses are generally used in a super-critical frequency range, during the change to which the stroke of the equipment is momentarily multiplied. In practice, the pairs of masses are first accelerated in opposite phases to the operation velocity, after which, by adjusting the phase difference the stroke is lengthened from zero to a desired value. If the electric motors, or their controls fail, or if there is a sudden total power outage, the rotational velocities of the pairs of masses decrease uncontrollably. When returning to the critical speed range, the stroke of the apparatus will then peak suddenly, breaking the equipment and possibly even the structures of the paper machine.
GB Pat. No. 836957 discloses a device, by which it might perhaps be possible to create sufficient oscillation to move a breast roll. The device is, in fact, proposed for moving, for example, a sieve. In addition, the structure of the rotating masses, and particularly their operating principle clearly differ from that described above. In the patent in question, the corresponding masses of the adjacent pairs of masses are mutually synchronized and only the mutual position of the masses of each pair of masses is altered using a complicated gear train. In other words, instead of altering the phase difference of the pairs of masses, what is altered is the mutual position of the masses, relative to the axis of rotation of the pair of masses. In addition, on top of the so-called center shaft there is a hollow shaft, to which the gear train is fitted. By rotating the relevant train relative to the center shaft, the mutual positions of the masses can be altered, without, however, altering the mutual phase difference of the pairs of masses. The synchronization ensures that the masses always rotate in the same phase. The device disclosed is complicated and the forces it creates are too small to move a breast roll. In addition, the drive train of the device cannot be adapted to the pairs of masses presently in use. In terms of control, the gear train is also slow and also unsuitable in practice, due, among other things, to the irreversible control.